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Switch working principle Apr 14, 2017

Work on the data link layer. The switch has a high bandwidth back bus and an internal exchange matrix. All the ports of the switch are hung on the back bus, and the control circuitry receives the packet, the processing port locates the Address table in memory to determine which port on which the NIC (NIC) hangs on the destination Mac (NIC's hardware address), the packet transmits quickly to the destination port through the internal Exchange matrix, the destination Mac does not exist, broadcasts to all ports, and the switch will "learn" the new address and add it to the internal MAC address table if the receiving port responds.

Using switches can also "fragment" the network, by comparing the MAC Address table, the switch allows only the necessary network traffic to pass through the switch. Filtering and forwarding of switches can effectively reduce conflict domains, but it cannot divide the network layer broadcast, the broadcast domain. Switches can be transmitted between multiple port pairs at the same time. Each port can be viewed as a stand-alone network segment, and the network devices connected to it enjoy all of the bandwidth alone, without competing with other devices. When node A sends data to node D, node B can send data to node C at the same time, and both transports enjoy the full bandwidth of the network, and have their own virtual connection. If this is a 10Mbps Ethernet switch, then the total flow of the switch is equal to the 2x10Mbps=20Mbps, and the use of 10Mbps shared hub, the total flow of a hub will not exceed 10Mbps.

In summary, the switch is a network device that is based on MAC address recognition and can complete encapsulation of forwarding packets. Switches can "learn" MAC addresses and store them in an internal address table by establishing a temporary swap path between the originator of the data frame and the target receiver, making the data frame reach the destination directly from the source address.